This invention relates to improvements to the process and plants using yeasts for the manufacture of beverages, such as beer, cider, wine and other alcoholized beverages, as well as of bakery products.
In the brewery field, it is known to stock an aqueous suspension of yeast or leaven resulting from a yeast culture produced in a propagator and/or from the harvesting of yeast previously used in the manufacture of wort, in a stocking container, from which a determined amount of yeast suspension is tapped and sent through means, such as a regulating pump, into a wort fermentation tank. The regulating pump is inserted in a pipe connecting the stocking container to the fermentation tank.
On the other hand, it is known that the quality of the yeast suspension contained in the stocking container is variable, so that the amount of said suspension to be introduced into the fermentation tank is also variable, in accordance with various factors, such as the compacity of the yeast, the fermentative power thereof and the like.
Various methods are known for adjusting the volume and the weight of the yeast suspension to be used in a fermentation tank having a given capacity. In one known method, a sample of yeast is taken from the stocking container and the compacity of said yeast is measured by centrifugation in a laboratory. According to another known method, a minimum amount of suspended yeast is injected into a fermentation tank and after said amount of yeast is uniformly distributed in the wort contained in the fermentation tank, a sample of yeast-containing fermented wort is taken and the number of yeast cells present in said sample is counted. Taking the results of this counting into account, an additional amount of yeast is introduced into the fermentation tank so as to ensure an optimum fermentation of the wort in said tank.
These known methods have several drawbacks. A common drawback of both methods is that they do not allow a qualitatively uniform fermentation of the wort. Moreover, the first known method, disclosed in the preceding paragraph, is time consuming, the sampling and the measurement of the compacity of the yeast suspension in a laboratory needing a lot of time, so that it is practically not possible to determine, within the prescribed time, the fermentative power of the used yeast. The second known process which involves a cell counting is not precise, since it does not take into account the dead cells as well as the cells, the fermentative power of which has been detrimentally effected.
This invention relates to a process and to a plant avoiding the drawbacks of the known methods.